Multichannel Cochlear Implantation Research Articles

Cochlear implant technology: past, present and future

<p indent=0mm>Cochlear implant (CI) technology can help the majority of patients with severe to profound sensorineural deafness to restore hearing. This technology was first launched in 1800 by the Italian physicist Alessandro Volta who found that electrical stimulation of the normal ear can produce hearing. In the 1960s, it began to enter the practical stage, and underwent technological development in two directions, single-channel and multi-channel. In 1979, the single-channel cochlear implant was successfully developed in Peking Union Medical College Hospital (PUMCH), and the first cochlear implantation in China was performed in 1980 in PUMCH. The first multi-channel cochlear implantation in China was also performed in PUMCH in May 1995. As the technology progressed, cochlear implantation with electric-acoustic stimulation (EAS), bilateral cochlear implantation, and robot-assisted cochlear implantation gradually went on stage. The first EAS cochlear implantation in China was performed in 2012 in PUMCH, and research on bilateral cochlear implantation in PUMCH ranks at the forefront in China. With increasing successful cases of surgery, the indications for cochlear implantation have gradually extended. In 2008, preoperative electrical stimulation auditory evoked potential technology was successfully developed in PUMCH, which is novel in China, and by which a large number of difficult and complex cases were successfully implanted with CI. Cochlear implantation for unilateral deafness and tinnitus and robot-assisted cochlear implantation have also been carried out worldwide. The first robot-assisted cochlear implantation in China was successfully performed in 2020 in Shanghai 9^th People’s Hospital. At the same time, the research of optical cochlear implant has entered the experimental stage. This paper summarizes the development of cochlear implant technology in China and abroad, the current technical expansion and the future development trend, to provide reference for its technological progress.

The history of cochlear implantation

The creation of cochlear implants has become possible owing to the collaboration in the field of neurophysiology, otorhinolaryngology, audiology, engineering, and psychoacoustics. The experiments carried out in the 1930s were not directly associated with the electrical stimulation of the auditory nerve but had a significant influence on the development of cochlear implants. The first attempt at direct electrical stimulation of the auditory nerve was performed in 1957 using a device that consisted of an active electrode and an implantable induction coil. A good discrimination of intensity but poor frequency discrimination of the acoustic stimuli in a deaf patient was achieved. In 1985, the cochlear implants were approved for the treatment of the adult patients and in 1990 for the children at the age under 2 years. Multi-channel cochlear implantation has been carried out in Russia since 1991 although the efforts to introduce singe-channel implantation were made in the 1980s. Nowadays, there are more than 8000 cochlear implant users in the Russian Federation. Cochlear implantation is performed in a number of clinical centres in several regions of the country funded from the federal budget.

Effects of Unilateral Cochlear Implantation on Balance Control and Sensory Organization in Adult Patients with Profound Hearing Loss.

Many studies were interested in the consequence of vestibular dysfunction related to cochlear implantation on balance control. This pilot study aimed to assess the effects of unilateral cochlear implantation on the modalities of balance control and sensorimotor strategies. Posturographic and vestibular evaluations were performed in 10 patients (55 ± 20 years) with profound hearing loss who were candidates to undergo unilateral multichannel cochlear implantation. The evaluation was carried out shortly before and one year after surgery. Posturographic tests were also performed in 10 age-matched healthy participants (63 ± 16 years). Vestibular compensation was observed within one year. In addition, postural performances of the patients increased within one year after cochlear implantation, especially in the more complex situations, in which sensory information is either unavailable or conflicting. Before surgery, postural performances were higher in the control group compared to the patients' group. One year after cochlear implantation, postural control was close to normalize. The improvement of postural performance could be explained by a mechanism of vestibular compensation. In addition, the recovery of auditory information which is the consequence of cochlear implantation could lead to an extended exploration of the environment possibly favoring the development of new balance strategies.

The effect of pre-operative developmental delays on the speech perception of children with cochlear implants

The objective of this study was to evaluate the relationship between developmental delays and speech perception in pre-lingually deafened cochlear implant recipients. This study was a retrospective review of patient charts conducted at a tertiary referral center. Thirty-five pre-lingually deafened children underwent multichannel cochlear implantation and habilitation at the Kyoto University Hospital Department of Otolaryngology-Head and Neck Surgery. A pre-operative cognitive-adaptive developmental quotient was evaluated using the Kyoto scale of psychological development. Post-operative speech performance was evaluated with speech perception tests two years after cochlear implantation. We computed partial correlation coefficients (controlled for age at the time of implantation and the average pre-operative aided hearing level) between the cognitive-adaptive developmental quotient and speech performance. A developmental delay in the cognitive-adaptive area was weakly correlated with speech perception (partial correlation coefficients for consonant-vowel syllables and phrases were 0.38 and 0.36, respectively). A pre-operative developmental delay was only weakly associated with poor post-operative speech perception in pre-lingually deafened cochlear implant recipients.

Unilateral Multi-Channel Cochlear Implantation Results in Significant Improvement in Quality of Life

To investigate the effects of unilateral multi-channel cochlear implant surgery on health-related quality of life and to determine if there is an age-related impact of cochlear implantation on these effects. Prospective study. Tertiary health-care center. The Short Form-36 survey (SF-36) was administered to determine the health-related quality of life of 283 age-stratified patients before and after cochlear implant surgery. Precochlear to postcochlear implantation changes in health-related quality of life as determined by the SF-36 questionnaire. There were significant increases in precochlear and postcochlear implantation scores for 5 of the 8 SF-36 survey domains: vitality, physical role functioning, mental health, emotional role functioning, and social functioning. Significant differences were found between age groups in the domains of social functioning, emotion role functioning, and mental health. Cochlear implant surgery significantly improves health-related quality of life as categorically stratified by the SF-36 questionnaire. These improvements were most evident in the mental health, emotional and social functioning, and physical functioning at work questions of the survey. Cochlear implant recipients younger than 65 years perceive a greater improvement in their level of energy, mental health, and social function compared with those older than 65 years.

Successful cochlear implantation in a patient with MNGIE syndrome

A 28-year-old woman with mitochondrial neurogastrointestinal encephalomyopathy (MNGIE syndrome) undergoing evaluation for multichannel cochlear implantation is described. The case history, diagnosis of mitochondrial disease, and assessment of the benefits of cochlear implantation are documented. The hearing level with cochlear implant and speech recognition were improved significantly for this patient. MNGIE syndrome is a rare congenital disorder of mitochondrial DNA (mt-DNA). It is crucial for the otolaryngologist to have awareness of MNGIE syndrome and other mitochondrial encephalomyopathies when patients present with sensorineural hearing loss (SNHL). Cochlear implantation can be recommended to patients with MNGIE syndrome and satisfactory results can be achieved.

Ophthalmological screening of a paediatric cochlear implant population: a retrospective analysis and 12-year follow-up

To determine the nature and prevalence of ophthalmological findings for a cohort of children in a paediatric cochlear implant program and to assist the clinician in devising an investigative plan for this population. Retrospective medical record review of children who underwent multichannel cochlear implantation at a tertiary care hospital between February 1996 and July 2008. In all, 141 children (mean age 28 months, range 16 months to 9 years) had complete medical record documentation consisting of orthoptic and opthalmological examination, including cycloplegic refraction. A total of 59 children (41.8%) had ocular abnormalities with refractive errors being the most common abnormality. Hypermetropia was the most common refractive error and was found in 21 children (14.8%). Strabismus was found in six patients, with constant esotropia being the most common. Ocular pathology (excluding refractive or muscle abnormalities) were found in nine patients (6.3%). Three patients had syndromes associated with ocular findings including Waardenburg and Usher syndrome. During the follow-up period, 14 children were fitted with prescription lenses, 3 had strabismus surgery, and 2 underwent ptosis. Routine orthoptic and ophthalmologic examination can be beneficial in the initial evaluation of children assessed for cochlear implants. Electroretinography is useful in evaluating children with unexplained congenital sensorineural hearing loss, suggestive symptoms including night blindness, unexplained reduction in visual acuity, or delayed motor milestones. Routine yearly follow-up may aid in the detection of changing refractive errors and the possibility of later-onset retinal degeneration.

Cochlear implantations in visually impaired patients

We retrospectively review the cases to evaluate the outcome of cochlear implantation (CI) in patients with severe-to-profound hearing loss and visual impairment (VI). Six adults with severe or profound hearing loss and significant VI underwent multichannel CI. Follow-up period ranged from 17 months to 7 years. Case history, etiology of visual and hearing loss, and benefit from CI were evaluated. To measure the outcomes, we selected the pure-tone thresholds with CI, the speech discrimination scores (SDS) using the Japanese video SDS system, the speech perception rates using the Japanese CD SDS system by monosyllable and word, and the open-set and closed sentence score using live voice. All the patients live happily after CI. There was no significant difference between the present six patients and the patients with profound hearing loss without VI in evaluations of hearing and quality of life. CI can play a significant rehabilitative role in patients with severe hearing loss and VI.

Multichannel Cochlear Implantation in the Scala Vestibuli

Sensorineural hearing loss resulting from otosclerosis, meningitis, chronic otitis media, autoimmune ear disease, and trauma can be associated with partial or total obstruction of the cochlear scalae. Multichannel cochlear implantation may be difficult in a cochlea with an obstructed scala tympani. The purpose of this study is to determine the safety and efficacy of scala tympani electrode insertion. Retrospective chart review. Academic medical center. Eight children and adults with profound sensorineural hearing loss who underwent cochlear implantation with known scala vestibuli electrode array insertion were subjects for this study. Eight study subjects underwent implantation: five with the Nucleus 24RCS (Contour) device and three with the Nucleus 24M device. Imaging findings, operative findings, and age-appropriate speech perception testing. All patients had full electrode insertion. Various obstructive patterns on computed tomography and magnetic resonance imaging were found, and there was a range of speech perception results. All but one patient improved based on age-appropriate monosyllabic word and sentence tests. Scala vestibuli multielectrode insertion is a viable alternative when scala tympani insertion is not possible because of abnormal anatomy or anatomical changes secondary to disease or previous implantation. We will also present an algorithm of options for decision making for implantation when encountering cochlear obstruction and difficult electrode insertion.

Cochlear implant outcomes in the elderly.

This study aimed to review cochlear implantation with respect to surgical and auditory outcomes in subjects aged 70 years and older. Retrospective chart review. Tertiary referral centers. Sixty-five patients aged 70 years or older at the time of implantation were compared to a group of patients aged <70 years. Patients underwent multichannel cochlear implantation with either the Clarion or Nucleus device. Presence or absence of surgical complications and auditory performance with open-set word and sentence recognition testing. In patients implanted at age 70 or older, significant improvement in speech understanding was demonstrated in performance scores using Consonant Nucleus Consonant words, Central Institute for the Deaf sentences, and Hearing in Noise Test sentences at 3, 6, and 12 months when compared to preimplantation scores. However, their performance was slightly poorer when compared to a control group of patients <70 years of age in the same measures at 3, 6, and 12 months. The elderly population showed significant improvement in auditory performance tests following cochlear implantation compared to their preimplantation scores but performed less well than younger patients.

Cochlear implantation in prelingually deaf children with ossified cochleae.

To evaluate the effects that degree of cochlear ossification has on performance of prelingually deafened children who receive cochlear implants. A matched-pairs analysis comparing speech perception results obtained 6 and 24 months after implant by children with ossified and nonossified cochleae. Additionally, long-term performance was evaluated in patients with follow-up periods longer than 24 months. Comparisons were also performed within the ossified cochleae group to determine if degree of cochlear ossification and surgical technique affected outcome with the cochlear implant. SETTING Large cochlear implant program in an academic tertiary care medical center. Twenty-one pairs of prelingually deaf children with and without cochlear ossification. Meningitis was the etiology of hearing loss in children with ossified cochleae. The control group had nonmeningitic etiology for the hearing loss. Multichannel cochlear implantation and routine postoperative auditory rehabilitation and performance evaluation. Speech perception category ratings based on scores obtained on a battery of closed- and open-set speech recognition tests 6 and 24 months after implant. Longer follow-up period is also reported. As a group, children with cochlear ossification showed significant improvement in their speech perception abilities 6 and 24 months after implant. Children with cochlear ossification performed at a significantly lower speech perception category than a group of matched controls with nonossified cochleae at both the 6- and 24-month postimplant intervals. With longer implant use, open-set speech recognition was possible in some children with ossification. Within-group analysis of the children with ossified cochleae revealed that degree of ossification and surgical procedure used for implantation did not significantly affect outcome. Prelingually deafened children with postmeningitic hearing loss and ossified cochleae receive significant benefit from cochlear implants. Their performance is frequently poorer, however, than children with nonossified cochleae.

Cochlear Implantation in a Patient with Mitochondrial Encephalopathy, Lactic Acidosis and Stroke-like Episodes Syndrome

Objective - The aim of this study was to investigate the usefulness of a Nucleus® CI24M cochlear implant in a patient with mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome. Material and methods - A 29-year-old woman with MELAS syndrome presented with sensorineural hearing loss and diabetes mellitus and underwent multichannel cochlear implantation. The follow-up period was 10 months. The case history, assessment of mitochondrial disease, indications for the cochlear implant and the benefits of cochlear implantation were evaluated. Results - Nine months after the surgery the patient could use the telephone and was quite satisfied with the improvement in communication due to the cochlear implant. Conclusion - Cochlear implantation can be recommended for patients with MELAS syndrome if they have residual retrocochlear function. Single photon emission computerized tomography was found to be very useful for evaluating retrocochlear function.

Multichannel cochlear implantation in radical mastoidectomy cavities.

We report on our experience in cochlear implantation in patients with radical mastoidectomy cavities. Study Design, Setting, and Methods: Retrospectively, records of patients from the Department of Otolaryngology, University of Parma between December 1991 and March 2000 were reviewed, and 6 postlingually deafened adults who received a cochlear implant in a radical cavity were identified. Speech performances were evaluated in terms of bisyllabic word and sentence recognition and common phrase comprehension. To date, with a follow-up of 1 to 9 years, no patient has experienced extrusion of electrodes or other local or intracranial complications. Mean bisyllabic word and sentence recognition scores were 74% and 80%, respectively. Mean comprehension score for common phrases was 86%. By obliterating and isolating the radical mastoidectomy cavity from the outer environment, patients who previously had undergone radical surgery of the middle ear can be safely implanted with satisfactory hearing results.

Nucleus multichannel cochlear implantation in partially ossified cochleas using the Steenerson procedure.

The purpose of this study was to report hearing results obtained in a group of subjects who received scala vestibuli implantation because of cochlear ossification and to compare these results to those in patients with scala tympani implantation. Retrospective analysis of consecutive cochlear implant procedures. Department of Otolaryngology, University of Parma. Five postlingually deafened adults with an electrode array placed into the scala vestibuli were compared with the speech performance of matched controls who had the electrode array inserted into the scala tympani. Measures included vowel and consonant speech identification scores, bisyllabic word and sentence speech recognition scores, and common phrases comprehension scores. No significant difference was detected on speech performances between the subjects with scala vestibuli implantation and the control group. Scala vestibuli implantation appears to be an excellent alternative in cases in which scala tympani is found to be not patent.

Surgery and Functional Outcomes in Deaf Children Receiving Cochlear Implants Before Age 2 Years

To examine the feasibility of cochlear implantation in children younger than 2 years regarding surgery and functional outcomes. Prospective study. Tertiary pediatric cochlear implant center. A consecutive sample of 12 children younger than 2 years at the time of cochlear implantation (8 boys and 4 girls). The cause of hearing loss was meningitis in 6 children and congenital in 6. Multichannel cochlear implantation using the Nucleus C124M (Cochlear Co, Sydney, Australia) device. Functional outcome was assessed using the Listening Progress Profile and the Categories of Auditory Performance. Perioperative and postoperative surgical complications and functional outcome. Eight children had a completely patent cochlea. Four children required a 3- to 5-mm drilling to reach the scala tympani because of ossification after meningitis. Full insertion was achieved in 11 patients; the other child received 18 electrodes. One patient had temporary facial nerve weakness; 2 others had wound edema and serous discharge that resolved with conservative management. In the longer term, 1 child experienced a single episode of acute otitis media; another had recurrent episodes of otitis media. Mean Listening Progress Profile scores increased from 1 to 42 and median Categories of Auditory Performance scores increased from 0 to 5 at 2 years postsurgery. Comparison with the scores in the 2- to 5-year group showed no significant differences. No significant tuning difficulties were experienced with all children. Cochlear implantation is feasible in children younger than 2 years without significant surgical complications or particular tuning difficulties. Functional results 2 years after implantation were as good as or better than those of children who underwent implantation between ages 2 and 5 years.

Histopathology of cochlear implants in humans.

The insertion of an intrascalar electrode array during cochlear implantation causes immediate damage to the inner ear and may result in delayed onset of additional damage that may interfere with neuronal stimulation. To date, there have been reports on fewer than 50 temporal bone specimens from patients who had undergone implantation during life. The majority of these were single-channel implants, whereas the majority of implants inserted today are multichannel systems. This report presents the histopathologic findings in temporal bones from 8 individuals who in life had undergone multichannel cochlear implantation, with particular attention to the type and location of trauma and to long-term changes within the cochlea. The effect of these changes on spiral ganglion cell counts and the correlation between speech comprehension and spiral ganglion cell counts were calculated. In 4 of the 8 cases, the opposite, unimplanted ear was available for comparison. In 3 of the 4 cases, there was no significant difference between the spiral ganglion cell counts on the implanted and unimplanted sides. In addition, in this series of 8 cases, there was an apparent negative correlation between residual spiral ganglion cell count and hearing performance during life as measured by single-syllable word recognition. This finding suggests that abnormalities in the central auditory pathways are at least as important as spiral ganglion cell loss in limiting the performance of implant users.

The effect of a multichannel cochlear implant on phoneme perception.

This study was done to investigate the effects of a multichannel cochlear implant on phoneme perception in Finnish-speaking postlingually deafened adults. Phoneme recognition was studied with 100 prerecorded nonsense syllables (open-set) presented at 70 dB SPL, auditorily only, in a free-field situation. Ten subjects were tested before implantation both with and without a hearing aid (HA), and 3, 6 and 12 months after switching on the implant. Before implantation without a HA, the subjects did not recognize vowels, consonants or syllables. Four of the subjects used a HA before implantation, and the mean recognition scores of these subjects were 34% for vowels, 28% for consonants and 13% for syllables. One year after switching on the implant, the mean recognition scores were 77% for vowels, 66% for consonants and 46% for syllables. According to phonological analysis vowels appear to be easier to perceive than consonants during the first stage after multichannel cochlear implantation.

Speech perception and functional benefit after multichannel cochlear implantation.

This study was done to investigate the effect of a multichannel cochlear implant on speech perception and the functional benefit of cochlear implantation in Finnish-speaking postlingually deafened adults. Fourteen subjects were enrolled. Sentence and word recognition were studied with open-set tests auditorily only. One year after implantation, the listening performance was assessed by case histories and interviews. Before implantation for subjects with a hearing aid, the mean recognition score was 38% for sentences and 17% for words. One year after switching on the implant, the mean recognition score was 84% for sentences and 70% for words. Before implantation, the majority of the subjects were not aware of environmental sounds and only a few were able to recognize some environmental sounds. One year after switching on the implant, the majority of the subjects were able to use the telephone with a familiar speaker. All the subjects were able to recognize speech auditorily only and had thus gained good functional benefit from the implant.

Speech perception after multichannel cochlear implantation in Finnish-speaking postlingually deafened adults.

This study was done to examine the short-term and long-term effects of multichannel cochlear implantation on speech perception in Finnish-speaking adults. The subjects comprise 20 adults. Pure-tone thresholds (0.125-8kHz), discrimination of phoneme quantity, sentence recognition, word recognition, phoneme recognition and listening performance were studied before and after implantation. After switch-on of the implant, the median pure-tone threshold values in the sound field were comparable to the level of mild hearing impairment. Most improvement in sentence recognition took place during the 6 months after the switch-on (mean score 74%). In word recognition, most improvement took place during the 12 months after the switch-on (mean score 66%), and clear improvement was noted even thereafter. In phoneme recognition, the performance of the subjects improved over the entire follow-up period, and 24 months after the switch-on the mean score was 52%. Individual variation was seen in the performance of the subjects. With 3 months of listening experience, all subjects were able to recognize some speech without speechreading, and they gained good functional benefit from the implant. The use of speech recognition tests with different degrees of difficulty is essential for the follow-up of adult cochlear implant subjects.

Postmeningitic Sclerosing and Ossifying Labyrinthitis

A considerable proportion of the candidates for multichannel cochlear implantation consists of patients with profound bilateral hearing loss caused by sclerosing and/or ossifying labyrinthitis as a complication of meningitis. The spread of bacteria and viruses from the meninges to the inner ear is generally thought to be either via the subarachnoid sheaths following the nerves in the internal acoustic canal, or more directly through the cochlear aqueduct. The infective stage can be followed by fibrosis of the labyrinth and later by new bone formation which may proceed to almost complete obliteration of the labyrinth. Computed tomography remains the first examination to perform in order to have a precise map of the inner ear and temporal bone anatomy as well as to depict any abnormality of the round window or calcification of the membranous labyrinth. In many centres CT is the first imaging modality chosen in the evaluation of cochlear-implant candidates, providing higher spatial resolution and unique information on skeletal structures. Temporal bone MR examination adds useful information before surgery because only thin T2-weighted sequences may depict focal or diffuse obliteration of the membranous labyrinth fluid space before calcification with a high degree of sensitivity. Moreover, MR plays a role in planning surgery, because a remaining postmeningitis labyrinthitis enhancement seems to predict a rapid evolution towards labyrinthine calcification.